Method and system for controlling interference between access nodes operating on adjacent TDD carriers with different TDD configurations

ABSTRACT

A first access node that is operating on a first TDD carrier having a first TDD configuration will determine that a second TDD carrier on which a proximate second access node is operating has a different, second TDD configuration, such that there is at least one time interval in which the first TDD carrier is downlink concurrently with the second TDD carrier being uplink. In response to at least this determination, the first access node will then transition to a mode in which, during the time interval, the first access node will operate with reduced transmission power on a frequency portion of the first TDD carrier that is closest in frequency to the second TDD carrier. Further, the first access node could allocate the lower-transmission-power frequency portion for use in transmission to served devices deemed to be in at least predefined threshold high quality coverage of the first access node.

REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. patent application Ser. No. 16/530,495,filed Aug. 2, 2019, the entirety of which is hereby incorporated byreference.

BACKGROUND

A typical cellular wireless system includes a number of access nodesconfigured to provide wireless coverage areas in which to serve userequipment devices (UEs) such as cell phones, tablet computers, trackingdevices, embedded wireless modules, and other wirelessly equippeddevices (whether or not user operated). In turn, each access node couldsit as a node on a core access network that includes entities such as anetwork controller and a gateway system providing connectivity with oneor more external transport networks such as the Public SwitchedTelephone Network (PSTN) and/or the Internet. With this arrangement, aUE within coverage of the system could engage in air interfacecommunication with an access node and could thereby communicate via theaccess node with various remote network entities or with other UEsserved by the access node.

Such a system could operate in accordance with a particular radio accesstechnology, with air-interface communications from the access nodes toUEs defining a downlink or forward link and air-interface communicationsfrom the UEs to the access nodes defining an uplink or reverse link.

Over the years, the industry has developed various generations of radioaccess technologies, in a continuous effort to increase available datarate and quality of service for end users. These generations have rangedfrom “1G,” which used simple analog frequency modulation to facilitatebasic voice-call service, to “4G”—such as Long Term Evolution (LTE),which now facilitates mobile broadband service using technologies suchas orthogonal frequency division multiplexing (OFDM) and multiple inputmultiple output (MIMO). And most recently, the industry is now exploringdevelopments in “5G” and particularly “5G NR” (5G New Radio), which mayuse a scalable OFDM air interface, advanced channel coding, massiveMIMO, beamforming, and/or other features, to support higher data ratesand countless applications, such as mission-critical services, enhancedmobile broadband, and massive Internet of Things (IoT).

In accordance with the radio access technology, each access node couldprovide service on one or more carriers, with each carrier spanning oneor more radio-frequency (RF) channels for carrying communicationswirelessly between the access node and UEs. In particular each carriercould be frequency division duplex (FDD), defining separate frequencychannels for downlink and uplink use, or time division duplex (TDD),defining a single frequency channel multiplexed over time betweendownlink and uplink use.

Each such frequency channel could be characterized by its position andwidth in RF spectrum, such as by a designated center frequency andbandwidth. Further, each channel could be structured to define variousphysical resources for carrying communications. For instance, under anexample radio access technology, each channel could be divided over timeinto frames, subframes, and timeslots, and symbol segments, and could bedivided over frequency into subcarriers. As a result, each channel coulddefine an array of time-frequency resource elements in which subcarrierscan be modulated to carry data communications. Further, within eachsubframe and timeslot, these resource elements could be divided intogroups defining physical resource blocks (PRBs) that can be allocated tocarry data on an as-needed basis.

Overview

When an access node operates on a TDD carrier, the carrier could bestructured with a particular TDD configuration (frame configuration)defining a sequence of equal-duration subframes and establishing whichsubframes are for downlink use and which subframes are for uplink use.Further, the TDD configuration may designate certain subframes asspecial subframes to help facilitate transition from downlink to uplinkoperation. Thus, a representative TDD configuration could establish foreach subframe per frame whether the subframe is a downlink subframe (D),an uplink subframe (U), or a special subframe (S).

Various TDD configurations could be feasible. In LTE, for instance, theair interface on a TDD carrier defines a continuum of 10-millisecondframes, each divided into ten 1-millisecond subframes, and LTE definesseven standard TDD configurations as set forth in Table 1.

TABLE 1 Subframe Number (0-9) TDD Configuration 0 1 2 3 4 5 6 7 8 9 0 DS U U U D S U U U 1 D S U U D D S U U D 2 D S U D D D S U D D 3 D S U UU D D D D D 4 D S U U D D D D D D 5 D S U D D D D D D D 6 D S U U U D SU U DNon-standard implementations and/or other radio access technologies maydefine other frame structures and other TDD configurations as well.

In practice, an access node that operates with a carrier having any suchTDD configuration could broadcast on the carrier a system informationmessage that specifies the carrier's TDD configuration, so that UEswithin coverage of the access node could determine the TDD configurationand operate accordingly. For instance, an access node could broadcast aSystem Information Block (SIB) message in subframe 0 of each frame andcould include in the SIB message a specification of the carrier's TDDconfiguration, such as a frame configuration (FC) number. Thus, a UEthat is within coverage of the access node on that carrier could readthat broadcast SIB message to determine the TDD configuration of thecell. Alternatively, a UE might determine the TDD configuration of acarrier in other ways, such as by monitoring to determine the subframesin which the access node transmits per frame.

The TDD configuration on an access node's carrier could be staticallyset by engineering design or the like. Or alternatively, the access nodecould dynamically vary the TDD configuration of the carrier to helpaccommodate varying traffic profiles. For example, at times when theaccess node serves heavier downlink traffic, the access node may use amore downlink-centric TDD configuration such as FC2, FC4, or FC5.Whereas, at times when the access node serves heavier uplink traffic,the access node may use a more uplink-centric TDD configuration such asFC0, FC1, or FC6.

One technical problem that can arise in some TDD implementations is thattwo access nodes positioned physically close to each other (e.g.,adjacent or collocated) may operate on respective carriers that areclose in frequency to each other but that use different TDDconfigurations than each other. In that situation, there would likely besome time intervals (e.g., subframes) that are downlink on one accessnode's carrier but are uplink on the other access node's carrier. And ineach such time interval, downlink transmission by one of the accessnodes could interfere with uplink reception by the other access node.

Although the two access nodes operate on different carriers than eachother, if those carriers are close enough in frequency to each other,spurious emission resulting from one access node's downlink transmission(e.g., due to imperfect filter roll-off, intermodulation distortion,and/or other factors) could extend into the adjacent frequency range ofthe other access node's carrier. And if that happens during an uplinktime interval on the other access node's carrier, that spurious emissioncould interfere with the other access node's reception of communicationsfrom served UEs.

This problem situation could arise in various scenarios.

As one example, a cellular wireless service provider might operate acell site with collocated access nodes that are configured to provideservice on different respective TDD carriers that are close to eachother in frequency. Without limitation, one such implementation could bewhere the cell site includes both a 4G LTE access node (evolved Node-B(eNB)) operating on a first TDD carrier and a 5G NR access node(next-generation Node-B (gNB)) operating on a second TDD carrier that isclose in frequency to the first TDD carrier and has a different TDDconfiguration than the first TDD carrier.

As another example, a cellular wireless service provider might operatetwo separate but physically close cell sites, one with an access nodeoperating on a first TDD carrier and another with an access nodeoperating on a second TDD carrier that is similarly close in frequencyto the first TDD carrier but has a different TDD configuration. And asstill another example, two cellular wireless service providers (e.g.,two competitor commercial providers, or perhaps a commercial providerand a public-safety provider) might operate respective nearby accessnodes, one operating on a first TDD carrier and the other operating on asecond TDD carrier also close in frequency to the first TDD carrier andhaving a different TDD configuration.

Disclosed herein is a method and system to help address this problem. Inaccordance with the disclosure, a first access node that is operating ona first TDD carrier having a first TDD configuration will determine thata second TDD carrier on which a proximate second access node isoperating has a different, second TDD configuration, such that there isat least one time interval (e.g., subframe) in which, concurrently, thefirst TDD carrier is downlink and the second TDD carrier is uplink. Inresponse to at least this determination, the first access node will thentransition to a mode in which, during the time interval, the firstaccess node will operate with reduced transmission power on a frequencyportion of the first TDD carrier that is closest in frequency to thesecond TDD carrier.

For instance, where the first TDD carrier is divided over frequency intoPRBs within the time interval at issue and if the first access nodenormally transmits at a default transmission power level, the firstaccess node could respond to the determination by transitioning to amode in which, during the time interval, the first access node operateswith reduced transmission power in certain PRBs closest in frequency tothe second TDD carrier but still operates with the default (non-reduced)transmission power in the remaining PRBs of the TDD carrier that arefarther away in frequency from the second carrier.

Further, in an example implementation, when the first access node hastransitioned to operate in this mode, the first access node could alsoresponsively apply a scheduling algorithm that limits allocation of thelower-power PRBs (for downlink transmission) to served UEs that are inrelatively strong coverage of the first access node, as such UEs may bebetter able than other UEs to receive the lower-power transmissions fromthe first access node.

These as well as other aspects, advantages, and alternatives will becomeapparent to those of ordinary skill in the art by reading the followingdetailed description, with reference where appropriate to theaccompanying drawings. Further, it should be understood that thedescriptions provided in this overview and below are intended toillustrate the invention by way of example only and not by way oflimitation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of a wireless communication systemin which various disclosed features can be implemented.

FIG. 2 is an illustration of an example time interval of two adjacentTDD carriers.

FIG. 3 is an illustration of spurious emission from one TDD carrierextending into a frequency range of another TDD carrier.

FIG. 4 Is an illustration of reduced-energy spurious emission resultingfrom transmission with reduced power on a frequency portion closest toan adjacent TDD carrier.

FIG. 5 is a flow chart depicting an example method in accordance withthe disclosure.

FIG. 6 is another flow chart depicting an example method in accordancewith the disclosure.

FIG. 7 is a simplified block diagram of an example access node operablein accordance with the disclosure.

DETAILED DESCRIPTION

An example implementation will now be described in the context of awireless communication system having a cell site that includes a 4G eNBoperating on at least one TDD carrier and a collocated 5G gNB operatingon at least another TDD carrier. It should be understood, however, thatthe principles disclosed herein could extend to apply in other scenariosas well, such as with respect to other RATs and/or other scenarios wheretwo access nodes are physically close enough to each other that onecould receive transmission from the other and where the access nodesoperate on different TDD carriers that are close enough in frequency toeach other that spurious emission from one access node might extend intothe frequency range of the other access node's carrier.

Further, other variations from the specific arrangements and processesdescribed are possible. For instance, various described entities,connections, functions, and other elements could be added, omitted,distributed, re-located, re-ordered, combined, or changed in other ways.In addition, it should be understood that operations described as beingperformed by one or more entities could be implemented in various ways,such as by a processing unit executing instructions stored innon-transitory data storage, along with associated circuitry or otherhardware, for instance.

FIG. 1 depicts an example cell site 12 that includes a 4G eNB 14 that isconfigured to provide 4G service on a 4G carrier 16, and a 5G gNB 18that is configured to provide 5G service a 5G carrier 20. These accessnodes could be collocated with each other at the cell site, possiblysharing a common antenna tower and other equipment, and could providecoverage in largely the same direction as each other, to defineoverlapping coverage in which UEs can receive both 4G service from the4G eNB 14 and 5G service from the 5G gNB 18. FIG. 1 then furtherillustrates a number of UEs 22 positioned within coverage of the twoaccess nodes.

In a representative implementation, carriers 16 and 20 are differentrespective TDD carriers, each having a respective center frequency andbandwidth in RF spectrum and thus each defining a respective range offrequency extending from a respective low-frequency end to a respectivehigh-frequency end.

The air interface respectively on each such carrier could be configuredas described above, being divided over time into frames, subframes,timeslots, and symbol time segments, and over frequency intosubcarriers, thus defining an array of air-interface resource elementsin which subcarriers can be modulated to carry data. And within eachsubframe, these resource elements could then be divided over frequencyinto groups defining the PRBs noted above, some or all of which theaccess node could be configured to allocate for use to carry data to orfrom served UEs on an as-needed basis.

Further, on each carrier, certain resource elements or PRBs could bereserved for special purposes. For instance, in each downlink subframe,resource elements within the first symbol time segments could bereserved to define a downlink control region for carrying downlinkcontrol signaling, resource elements in the remaining symbol timesegments could be reserved to define a downlink shared-channel regionfor carrying scheduled data communications in PRBs, and certain resourceelements distributed in frequency and time throughout the subframe couldbe reserved to carry a broadcast reference signal that UEs can measureto evaluate coverage quality on the carrier. And in each uplinksubframe, certain PRBs could be reserved to define an uplink controlregion for carrying uplink control signaling, and other PRBs could bereserved to define an uplink shared-channel region for carryingscheduled data communications in PRBs. Other air-interfaceconfigurations are possible as well.

4G and 5G could also differ from each other in various ways now known orlater developed. For instance, one might implement variable subcarrierspacing and the other might have fixed subcarrier spacing, one mightsupport dynamic (flexible) TDD configuration and the other might supportonly static (fixed) TDD configuration, one might have different symboltime segments than the other, and/or one might make different use ofMIMO technologies than the other, among other possibilities.

As further shown, the example 4G eNB and 5G gNB are each connected witha common core network 24, which could be an Evolved Packet Core (EPC)network or Next Generation Core (NGC) network for instance. In theexample shown, the core network includes a serving gateway (SGW) 26, apacket data network gateway (PGW) 28, and a mobility management entity(MME) 30.

In this arrangement, the 4G eNB and 5G gNB might each have an interfacewith the SGW, the SGW might have an interface with the PGW, and the PGWmight provide connectivity with a transport network 32. In addition, atleast the 4G eNB might have an interface with the MME, and the MME mighthave an interface with the SGW, so that the MME could coordinate setupof bearer connections for UEs to enable the UEs to engage in packet-datacommunication via 4G and 5G. Further, the 4G eNB and 5G gNB may have aninter-access-node interface enabling them to engage in signaling witheach other.

This example system might support UEs connecting and being served invarious ways by the 4G eNB and by the 5G gNB. For example, the systemmight support UEs connecting initially with the 4G eNB via the 4Gcarrier 16 and might support then setting up of dual-connectivity forsuch UEs to be served concurrently by the 4G eNB via the 4G carrier 16and the 5G gNB via the 5G carrier 20. Further, the cell site mightsupport UEs separately connecting with and being served by the 4G eNBvia the 4G carrier 16 and/or the 5G gNB via the 5G carrier 20. Otherexamples may be possible as well.

With this or other arrangements, a UE may thus establish an airinterface connection with an access node on the access node's carrier.Further, the UE may engage in attach signaling with the MME to registerfor service with the network, and the MME may coordinate setup for theUE of a data bearer including access-bearer portion extending betweenthe access node and the SGW/PGW and a radio bearer portion extendingover the air between the access node and the UE.

Once the UE is connected with an access node on a carrier and isregistered for service, the access node could then serve the UE withwireless packet-data communications. For instance, when the core network24 has data to transmit to the UE, the access node could select one ormore downlink PRBs of an upcoming downlink subframe for carrying thedata, and in that subframe the access node could transmit to the UE ascheduling directive designating the PRB(s) and could transmit the datato the UE in the designated PRB(s). And when the UE has data to transmitto the core network, the UE could transmit a scheduling request to theaccess node, the access node could responsively select one or moreuplink PRBs of an upcoming uplink subframe for carrying the data andcould transmit to the UE in a preceding downlink subframe a schedulingdirective designating the PRB(s), and the UE could then transmit thedata to the access node in the designated PRB(s).

In addition, while the UE is being served by the access node on a givencarrier, the UE may regularly evaluate the quality of its coverage fromthe access node on that carrier and may report the coverage quality foruse in various ways. For example, the UE may report when the coveragestrength on the carrier becomes threshold low, which might result intriggering handover of the UE to another access node. And as anotherexample, the UE might regularly report channel quality, and the accessnode might use the reported channel quality as a basis to set anappropriate modulation and coding scheme for use in carrying data overthe air between the access node and the UE.

As noted above, difficulty could arise with the arrangement shown inFIG. 1 if TDD carriers 16 and 20 are close enough in frequency to eachother and if the carriers have different TDD configurations than eachother such that a downlink time interval on one carrier exists at thesame time as an uplink time interval on the other carrier. Though staticor dynamic settings of either carrier's TDD configuration or of bothcarriers' TDD configurations, for instance, it may be the case that the4G carrier 16 has a downlink subframe that overlaps partially orcompletely in time with an uplink subframe of 5G carrier 20, or viceversa.

FIG. 2 illustrates this scenario by way of example, plotting time versusfrequency and depicting a 1-millisecond time interval of adjacentcarriers 16 and 20. As shown in this example, 4G carrier 16 has adefined frequency range extending from a low-end frequency F1 to ahigh-end frequency F2, and 5G carrier 20 has a defined frequency rangeextending from a low-end frequency F3 to a high-end frequency F4. Eachof these carriers is further shown divided over its respective frequencyrange into example PRBs. These carriers are “adjacent” to each other inthat spurious emission resulting from transmission on one carrier mightextend at least somewhat into the other carrier's frequency range, evenif there may be a guard band or one or more intervening carriers.

As noted above, spurious emission could result from imperfect filterroll-off, intermodulation distortion, and/or one or more other factors.For example, an access node may be equipped with an RF filter to helpconstrain the frequency range of its transmission to within certainlicensed frequency and perhaps particularly the frequency range(s) ofthe carrier(s) on which the access node is configured to operate.However, the filter will likely be imperfect, passing harmonics and/orother signals outside of that range. Further, to the extent the accessnode processes transmissions on multiple subcarriers and/or multiplecarriers, those transmissions might combine with each other to produceintermodulation products or the like that might also fall outside of theaccess node's operating frequency range.

FIG. 3 illustrates how this spurious emission problem could play outbetween carrier's 16 and 20. In particular, FIG. 3 plots transmissionpower versus frequency in a scenario where carrier 16 is downlink andcarrier 20 is uplink. Here, while 4G eNB 12 may have an RF filter thatseeks to limit the frequency of its transmission to be no higher thanthe high-end frequency F2 of carrier 16, while 4G eNB 12 is transmittingwith a default transmission power level P_(default) on carrier 16, the4G eNB 12 may provide spurious emission 34 in the form of a signal thatdecays down from power level P_(default) as frequency increases.

Unfortunately, this spurious emission 34 could interfere with aconcurrent effort by 5G gNB 18 to receive communications from one ormore UEs on carrier 20. In particular, this emission from 4G eNB 12could be received by 5G gNB 18 and could create difficulty for 5G gNB 18receiving UE communications at the same time. For instance, the emissionfrom 4G eNB 12 could reduce a signal-to-noise-plus-interference (SINR)at the receiver of 5G gNB 18, which may lead to failed reception,retransmission, and other issues.

In this example scenario, the present disclosure provides for addressingthis problem by having 4G eNB 12 dynamically reduce the power of itstransmission on a frequency portion of carrier 16 that is closest infrequency to adjacent carrier 20, particularly in any such time intervalwhere carrier 16 is downlink and carrier 20 is uplink.

By way of example, 4G eNB 12 could identify a time interval when itsserving carrier 16 is downlink and adjacent carrier 20 of 5G gNB 18 isuplink, and based on identifying that time interval, 4G eNB 12 couldreduce its transmission power in one or more PRBs at the high end ofcarrier 16, while continuing to operate with its default transmissionpower in other PRBs of carrier 16. Namely, 4G eNB 12 could select a setof one or more such PRBs based on the PRB(s) being at the high end ofcarrier 16, and 4G eNB 12 could transition to a mode in which it uses areduced transmission power P_(reduced) rather than its defaulttransmission power P_(default) for transmission on the selected PRB(s),while continuing to operate with its default transmission power on PRBsof carrier 16 that are more distant in frequency from carrier 20.

4G eNB 12 could make this transmission-power adjustment selectively on aper PRB basis by dynamically controlling the gain of a power amplifierthat 4G eNB 12 uses for RF transmission. For instance, the 4G eNB 12could configure the power amplifier to amplify subcarriers in theidentified PRB(s) less than subcarriers in other PRBs of carrier 16.

FIG. 4 shows a possible impact of this power reduction on the level ofspurious emission from 4G eNB 12. As shown in FIG. 4, because thetransmission power on one or more PRB(s) at the high end of carrier 16is reduced, the power level of associated spurious emission 36 isreduced, thus creating less interference if any within the frequencyrange of carrier 20. Optimally, this reduced interference on carrier 20may therefore enable 5G gNB 18 to better receive and process UEtransmissions on carrier 20 during the time interval at issue.

In an example implementation, the default transmission power P_(default)that 4G eNB 12 uses for transmission on carrier 16 may be on the orderof 43 decibel-milliwatts (dBm), and the 4G eNB 12 could reduce itstransmission power on the select PRB(s) to a level that approaches thatlikely used for uplink transmission by UEs to 5G gNB 18, such as 26 dBmor 26 dBm for instance. By having 4G eNB 12 use a UE-like transmissionpower on the select PRB(s) close in frequency to carrier 20, 5G gNB 18may be better able to withstand the resulting spurious emission.

The process described so far may assume that 4G eNB 12 knows about thetime interval in which carrier 16 will be downlink and carrier 20 willbe uplink and further knows that carrier 20 is close in frequency tocarrier 16, carrier 20 is an operating carrier of 5G gNB 18, and 5G gNB18 is physically close to 4G eNB 12 (e.g., that a receive antennastructure of 5G gNB 18 is close enough to a transmit antenna structureof 4G eNB 12 such that signals transmitted by 4G eNB 12 could bereceived by 5G gNB 18.

In practice, 4G eNB 12 might learn some or all of this information basedon access-node neighbor data provisioned at 4G eNB 12 and/or otherwiseaccessible to 4G eNB 12 (possibly from a shared element managementsystem (EMS) or the like). Alternatively or additionally, 4G eNB 12could learn some of this information based on inter-access-nodesignaling between 4G eNB 12 and 5G gNB 18.

Through these or other mechanisms, for instance, 4G eNB 12 might learnthat 5G gNB 18 is physically close and that 5G gNB 18 is operating oncarrier 20, and 4G eNB could compare carrier 20 with its own operatingcarrier 16 to determine that the two are adjacent in frequency.

Further, through similar mechanisms, 4G eNB 12 might learn the current(static or dynamically set) TDD configuration of carrier 20 on which 5GgNB is operating, and 4G could compare that TDD configuration with thecurrent (static or dynamically set) TDD configuration of its ownoperating carrier 16 to identify a time interval in which carrier 16 isdownlink and carrier 20 is uplink. Alternatively, 4G eNB 12 mightdetermine the TDD configuration of carrier 20 in another manner, such asby scanning carrier 20 to determine the subframes per frame in which 5GgNB transmits, as downlink subframes.

Note also that the present process could apply with various types oftime intervals. In one example, for instance, the process could apply ona subframe basis, such as across a 1-millisecond subframe in whichcarrier 16 is downlink and carrier 20 is uplink. And alternatively oradditionally, the process the could apply with respect to a portion of asubframe, such a time interval in which carrier 12 defines a downlinkportion (DwPTS) of a special subframe and/or when carrier 20 defines anuplink portion (UpPTS) of a special subframe. Still further, note thatframe timing between carrier 16 and carrier 20 may or may not beperfectly synchronized. If it is not perfectly synchronized, 4G eNB 12could engage in further signaling to more specifically identify a timeinterval when carrier 16 is downlink and carrier 20 is uplink, tofacilitate carrying out the present process.

As further noted above, in an example implementation of the presentprocess, when the 4G eNB 12 is operating in the mode in which it usesreduced transmission power on select PRB(s) close in frequency tocarrier 20, the 4G eNB 12 could then responsively limit allocation ofthe lower-power PRB(s) to UEs that are in threshold good coverage of 4GeNB 12, as those UEs could be best able to receive the lower-powertransmission from the 4G eNB 12.

To facilitate this for a given served UE, the 4G eNB 12 could determinebased on coverage quality reports from the UE whether the UE's coveragequality is at least as high as a predefined threshold deemed to be highenough for this purpose. If so, then based at least on thatdetermination and based on the lower-power PRB(s) being lower-powerPRB(s), the 4G eNB 12 could allocate at least the lower-power PRB(s) fortransmission of data to the UE. Whereas, if not, then based at least onthat determination and based on the lower-power PRB(s) being lower-powerPRB(s), then 4G eNB 12 could forgo allocating the lower-power PRB(s) fortransmission to the UE and may instead allocate one or more other PRBsfor transmission to the UE.

FIG. 5 is a flow chart depicting a method that could be carried out inaccordance with the present disclosure to help control interferencebetween access nodes or other serving entities operating on adjacent TDDcarriers with different TDD configurations. This method could be carriedout by or for a first such access node, to control transmission by thefirst access node on a TDD carrier having a first frequency range andhaving a first TDD configuration that defines a first sequence of uplinkand downlink time intervals (e.g., subframes and/or portions thereof,among other possibilities). For instance, in the arrangement of FIG. 1,the method could be carried out by 4G eNB 12.

As shown in FIG. 5, at block 50, the method includes detecting apotential for interference on a second TDD carrier on which a proximatesecond access node is operating, in a scenario where the second TDDcarrier is adjacent in frequency to the first TDD carrier and has asecond TDD configuration different than the first TDD configuration, thedetecting including determining that there is at least one time intervalin which the second TDD carrier is uplink concurrently with the firstTDD carrier being downlink. At block 52, the method then includes,responsive to at least the detecting, the first access node operating ina differential power mode during the determined time interval, includingusing a first transmission power on a first frequency portion of thefirst TDD carrier that is closest in frequency to the second TDD carrierwhile using a second transmission power on a second frequency portion ofthe first TDD carrier that is farther away in frequency from the secondTDD carrier, the first transmission power being lower than the secondtransmission power.

In line with the discussion above, this method could additionallyinclude, responsive to at least the first access node operating in thedifferential power mode, the first access node allocating the firstfrequency portion of the first TDD carrier in the determined timeinterval to one or more served devices based at least on (i) the one ormore served devices being in at least predefined threshold high qualitycoverage of the first access node and (ii) the first access node usingthe first, lower transmission power on the first frequency portion.

In addition, as discussed above, the act of detecting the potential forinterference on the second TDD carrier could also include determiningthat the second TDD carrier is adjacent in frequency to the first TDDcarrier, determining that the second TDD carrier has the second TDDconfiguration different than the first TDD configuration, and/ordetermining that the second access node is proximate to the first accessnode (e.g., that the two are collocated or otherwise close enough forthe presently addressed issue to arise).

Further, as discussed above, either or each of the first TDDconfiguration of the first TDD carrier or the second TDD configurationof the second TDD carrier could be dynamically configured and/or couldbe statically configured. And in either case, the second TDDconfiguration could define a second sequence of uplink and downlink timeintervals, and the act of determining that there is the at least onetime interval in which the second TDD carrier is uplink concurrentlywith the first TDD carrier being downlink could involve comparing thefirst sequence with the second sequence.

Still further, as discussed above, the first TDD carrier could bedivided over the first frequency range into PRBs, and the second carriercould have a second frequency range. And in that case, the firstfrequency portion of the first TDD carrier closest in frequency to thesecond TDD carrier could be a first one or more of the PRBs selectedbased on the one or more PRBs being closest in frequency to the secondfrequency range of the second TDD carrier, and the second frequencyportion of the first TDD carrier could include a second one or more ofthe PRBs farther away in frequency than the first one or more PRBs fromthe second frequency range of the second TDD carrier.

And yet further, the first access node and second access node could becollocated and/or operated by a common wireless service provider,perhaps with one operating on one radio access technology and the otheroperating on a different radio access technology. Or the first accessnode and the second access node could be operated by differentrespective wireless service providers.

FIG. 6 is another flow chart depicting a method that could be carriedout in accordance with the present disclosure to control transmission bya first access node on a first TDD carrier having a first frequencyrange and having a first TDD configuration that defines a first sequenceof uplink and downlink time intervals, where the first access node isconfigured to transmit with a default transmission power.

As shown in FIG. 6, at block 60, the method includes detecting apotential for interference on a second TDD carrier on which a proximatesecond access node is operating and that is adjacent in frequency to thefirst TDD carrier, the detecting including determining that the secondTDD carrier has a second TDD configuration with at least one uplink timeinterval that is concurrent with at least one downlink time interval ofthe first TDD configuration of the first TDD carrier.

At block 62, the method then includes, responsive to at least thedetecting, the first access node operating in a differential power modein which, during the downlink time interval of the first TDDconfiguration of the first TDD carrier, (a) the first access node usesreduced transmission power on a first frequency portion of the first TDDcarrier that is closest in frequency to the second TDD carrier whileusing the default transmission power in a second frequency portion ofthe first TDD carrier and (b) the first access node allocates the firstfrequency portion of the first TDD carrier in the downlink time intervalto one or more served devices based at least on (i) the one or moreserved devices being in at least predefined threshold high qualitycoverage of the first access node and (ii) the first access node usingthe reduced transmission power on the first frequency portion.

Various features described above can be implemented in this context, andvice versa.

For example, the act of detecting the potential for interference on thesecond TDD carrier could include determining that the second TDD carrieris adjacent in frequency to the first TDD carrier and that the secondaccess node is proximate to the first access node.

Further, the act of determining that the second TDD carrier has thesecond TDD configuration with the at least one uplink time interval thatis concurrent with the at least one downlink time interval of the firstTDD configuration of the first TDD carrier could involve determiningthat the at least one uplink time interval of the second TDDconfiguration is concurrent with the at least downlink time interval ofthe first TDD configuration. For instance, the second TDD configurationcould define a second sequence of uplink and downlink time intervals,and determining that the at least one uplink time interval of the secondTDD configuration is concurrent with the at least downlink time intervalof the first TDD configuration could involve comparing the firstsequence with the second sequence.

Still further, the act of determining that the second TDD carrier hasthe second TDD configuration could be based on reference to neighbordata and/or based on monitoring of transmission from the second accessnode.

And as discussed above, the first TDD carrier could be divided over thefirst frequency range into PRBs, the second carrier could have a secondfrequency range, the first frequency portion of the first TDD carrierclosest in frequency to the second TDD carrier could be one or more ofthe PRBs closest in frequency to the second frequency range of thesecond TDD carrier, and the second frequency portion could include oneor more of the PRBs farther away in frequency from the second frequencyrange of the second TDD carrier.

FIG. 7 is a simplified block diagram of an example first access node,such as 4G eNB 12, showing some of the components that could be includedin the access node in a non-limiting example implementation. As shown,the example first access node includes a wireless communicationinterface 70, a backhaul communication interface 72, and a controller74, which could be integrated together in various ways (e.g., on achipset) and/or interconnected by a system bus, network, or othercommunication mechanism 76 as shown.

The wireless communication interface 70 could include a transceiverconfigured to serve UEs in accordance with one or more radio accesstechnologies and could comprise one or more radios, amplifiers, and RFfilters, as well as an antenna structure for transmitting and receiving.Through the wireless communication interface 70, the first access nodecould engage in air-interface communication operating on a first TDDcarrier having a first frequency range and having a first TDDconfiguration that defines a first sequence of uplink and downlink timeintervals as discussed above.

The backhaul wireless communication interface 72 could then comprise awired or wireless network communication module, such as an Ethernetinterface, through which to communicate with other entities, perhapswith the second access node and/or with one or more other entities on orvia a core network.

Further, the controller 74 could comprise a processing unit (e.g., oneor more processing units such as microprocessors and/or specializedprocessors), non-transitory data storage (e.g., one or more volatileand/or non-volatile storage components, such as magnetic, optical, orflash storage), and program instructions stored in the data storage andexecutable by the processing unit to carry out, or cause the access nodeto carry out, various operations as described herein. Various featuresdiscussed above can be implemented in this context, and vice versa.

Further, the present disclosure also contemplates a non-transitorycomputer-readable medium having encoded thereon (e.g., storing,embodying, containing, or otherwise incorporating) program instructionsexecutable to cause a processing unit to carry out operations such asthose described above.

Exemplary embodiments have been described above. Those skilled in theart will understand, however, that changes and modifications may be madeto these embodiments without departing from the true scope and spirit ofthe invention.

We claim:
 1. A method to control transmission by a first access node ona first time division duplex (TDD) carrier having a first frequencyrange and having a first TDD configuration that defines a first sequenceof uplink and downlink time intervals, the method comprising: detectinga potential for interference on a second TDD carrier on which aproximate second access node is operating, wherein the second TDDcarrier is adjacent in frequency to the first TDD carrier and has asecond TDD configuration different than the first TDD configuration,wherein the detecting includes determining that there is at least onetime interval in which the second TDD carrier is uplink concurrentlywith the first TDD carrier being downlink; and responsive to at leastthe detecting, operating by the first access node in a differentialpower mode during the determined time interval, including using a firsttransmission power on a first frequency portion of the first TDD carrierthat is closest in frequency to the second TDD carrier while using asecond transmission power on a second frequency portion of the first TDDcarrier that is farther away in frequency from the second TDD carrier,the first transmission power being lower than the second transmissionpower.
 2. The method of claim 1, wherein the detecting further includesdetermining that the second TDD carrier is adjacent in frequency to thefirst TDD carrier and determining that the second TDD carrier has thesecond TDD configuration different than the first TDD configuration. 3.The method of claim 1, wherein the detecting further includesdetermining that the second access node is proximate to the first accessnode.
 4. The method of claim 1, wherein at least one of the first TDDconfiguration of the first TDD carrier or the second TDD configurationof the second TDD carrier is dynamically configured.
 5. The method ofclaim 1, wherein the second TDD configuration defines a second sequenceof uplink and downlink time intervals, and wherein determining thatthere is the at least one time interval in which the second TDD carrieris uplink concurrently with the first TDD carrier being downlinkcomprises: comparing the first sequence with the second sequence.
 6. Themethod of claim 1, wherein the first TDD carrier is divided over thefirst frequency range into physical resource blocks (PRBs), wherein thesecond TDD carrier has a second frequency range, wherein the firstfrequency portion of the first TDD carrier closest in frequency to thesecond TDD carrier is one or more of the PRBs closest in frequency tothe second frequency range of the second TDD carrier, and wherein thesecond frequency portion of the first TDD carrier comprises one or moreof the PRBs farther away in frequency from the second frequency range ofthe second TDD carrier.
 7. The method of claim 1, wherein the firstaccess node and second access node are collocated and operated by acommon wireless service provider.
 8. The method of claim 7, wherein thefirst access node provides service on the first TDD carrier according toa first radio access technology (RAT) rather than a second RAT, andwherein the second access node provides service on the second RAT ratherthan the first RAT.
 9. The method of claim 1, wherein the first accessnode and second access node are operated by different respectivewireless service providers.
 10. A method to control transmission by afirst access node on a first time division duplex (TDD) carrier having afirst frequency range and having a first TDD configuration that definesa first sequence of uplink and downlink time intervals, wherein thefirst access node is configured to transmit with a default transmissionpower, the method comprising: detecting a potential for interference ona second TDD carrier on which a proximate second access node isoperating and that is adjacent in frequency to the first TDD carrier,wherein the detecting includes determining that the second TDD carrierhas a second TDD configuration with at least one uplink time intervalthat is concurrent with at least one downlink time interval of the firstTDD configuration of the first TDD carrier; and responsive to at leastthe detecting, operating by the first access node in a differentialpower mode in which, during the downlink time interval of the first TDDconfiguration of the first TDD carrier, the first access node usesreduced transmission power on a first frequency portion of the first TDDcarrier that is closest in frequency to the second TDD carrier whileusing the default transmission power in a second frequency portion ofthe first TDD carrier.
 11. The method of claim 10, wherein the detectingfurther includes determining that the second TDD carrier is adjacent infrequency to the first TDD carrier and that the second access node isproximate to the first access node.
 12. The method of claim 10, whereindetermining that the second TDD carrier has the second TDD configurationwith the at least one uplink time interval that is concurrent with theat least one downlink time interval of the first TDD configuration ofthe first TDD carrier comprises: determining that the at least oneuplink time interval of the second TDD configuration is concurrent withthe at least downlink time interval of the first TDD configuration. 13.The method of claim 12, wherein the second TDD configuration defines asecond sequence of uplink and downlink time intervals, and whereindetermining that the at least one uplink time interval of the second TDDconfiguration is concurrent with the at least downlink time interval ofthe first TDD configuration comprises: comparing the first sequence withthe second sequence.
 14. The method of claim 10, wherein determiningthat the second TDD carrier has the second TDD configuration is based onreference to neighbor data.
 15. The method of claim 10, whereindetermining that the second TDD carrier has the second TDD configurationis based on monitoring of transmission from the second access node. 16.The method of claim 10, wherein the first TDD carrier is divided overthe first frequency range into physical resource blocks (PRBs), whereinthe second TDD carrier has a second frequency range, wherein the firstfrequency portion of the first TDD carrier closest in frequency to thesecond TDD carrier is one or more of the PRBs closest in frequency tothe second frequency range of the second TDD carrier, and wherein thesecond frequency portion comprises one or more of the PRBs farther awayin frequency from the second frequency range of the second TDD carrier.17. A first access node comprising: a wireless communication interfacethrough which the first access node engages in air-interfacecommunication operating on a first time division duplex (TDD) carrierhaving a first frequency range and having a first TDD configuration thatdefines a first sequence of uplink and downlink time intervals; abackhaul communication interface; and a controller configured to controltransmission by a first access node on the first TDD carrier, whereinthe controller is configured to detect a potential for interference on asecond TDD carrier on which a proximate second access node is operating,wherein the second TDD carrier is adjacent in frequency to the first TDDcarrier and has a second TDD configuration different than the first TDDconfiguration, wherein the detecting includes determining that there isat least one time interval in which the second TDD carrier is uplinkconcurrently with the first TDD carrier being downlink, and wherein thecontroller is configured to respond to at least the detecting by causingthe first access node to operate in a differential power mode during thedetermined time interval, wherein, in the differential power mode, thefirst access node uses a first transmission power on a first frequencyportion of the first TDD carrier that is closest in frequency to thesecond TDD carrier while using a second transmission power on a secondfrequency portion of the first TDD carrier that is farther away infrequency from the second TDD carrier, the first transmission powerbeing lower than the second transmission power.
 18. The first accessnode of claim 17, wherein the detecting further includes determiningthat the second TDD carrier is adjacent in frequency to the first TDDcarrier and determining that the second TDD carrier has the second TDDconfiguration different than the first TDD configuration.
 19. The firstaccess node of claim 17, wherein the detecting further includesdetermining that the second access node is proximate to the first accessnode.
 20. The first access node of claim 17, wherein the first TDDcarrier is divided over the first frequency range into physical resourceblocks (PRBs), wherein the second TDD carrier has a second frequencyrange, wherein the first frequency portion of the first TDD carrierclosest in frequency to the second TDD carrier is one or more of thePRBs closest in frequency to the second frequency range of the secondTDD carrier, and wherein the second frequency portion of the first TDDcarrier comprises one or more of the PRBs farther away in frequency fromthe second frequency range of the second TDD carrier.